Somatostatin is a tetradecapeptide having the structure: ##STR2## and has the properties of inhibiting the release of growth hormone, inhibiting the release of insulin and glucagon and reducing gastric secretion. This lack of specificity of the biological activity of somatostatin has led to an intensive search for analogs which exhibit a more specific biological activity. Somatostatin itself has a short duration of action because it is inactivated, inter alia, by aminopeptidases and carboxypeptidases present in vivo. This problem of the short duration of action has been partially solved in the prior art by preparing derivatives of somatostatin which have low solubility, thus attaining a slow release on subcutaneous injection. Once dissolved, however, the derivatives are no more stable to inactivation by aminopeptidases and carboxypeptidases than somatostatin itself. The present invention provides somatostatin analogs having no material affect on gastric secretion and a longer duration of action and a novel method for preparing said analogs.
The present invention further provides somatostatin analogs which are easier to prepare because they contain only 26 atoms in the peptide backbone.